My early pies were done with bread flour that browns at lower temps, thus so of those pictures may hide the lower temps achieved without insulation.
The insulation and stucco is definitely worth it for the following reasons.
a) the fuel use is dramatically lower insulated.
b) the exterior of an uninsulated oven is very high and would burn accidental brushers by, such as children, even many hours after using it.
c) while high temps could be reached uninsulated, is is very uneven, unstable, and requires a large fire.
d) insulating it wasn't very expensive. I believe the entire oven and stand could be done for under $1000.
e) The stucco protects the insulation but will crack if you build it without a compressible layer such as ceramic blanket. So plan on using a cover if you do it that way.
So to some up, uninsulated was fun for experimenting but if you are going to continue to use it you are much better off insulating it. It was a lot of work but a ton of fun too